Rabobank is the biggest backer of Dutch professionalcycling, with total sponsorship worth 15 million euros ($20million) a year in a nation with as many bikes as people.

Its decision shows the damage being done to cycling afterthe U.S. Anti-Doping Agency (USADA) said seven times Tour deFrance winner Armstrong took part in and organised asophisticated doping scheme on his way to success.

"We are no longer convinced that the internationalprofessional world of cycling can make this a clean and fairsport. We are not confident that this will change for the betterin the foreseeable future," Bert Bruggink, Rabobank boardmember, said in a statement.

"The USADA report was the final straw," he added later in apress conference televised live in the Netherlands.

"The international sport of cycling is not only sick, thesickness goes up to the highest levels," he said.

Sportswear company Nike and brewer Anheuser-Busch dropped their sponsorship of Armstrong this week, andthe sport must show it can tackle doping effectively to preventmore of its backers from quitting.

The International Cycling Union (UCI), the sport's governingbody, has yet to rule on the USADA's report into Armstrong andhas been criticised for dragging its feet.

Armstrong, a 41-year-old cancer survivor, has always deniedtaking banned substances but has decided not to challenge theUSADA charges.

American rider Levi Leipheimer, who rode for Rabobankbetween 2002 and 2004, was sacked this week by the Quick-StepCycling Team after admitting to the USADA investigation that hetook banned substances.

Leipheimer, 38, was one of 11 former team mates to testifyagainst Armstrong.

COMMERCIAL DAMAGE

Another sponsor, SKINS, which is a partner of the Rabobankteam, said on Thursday it would reconsider its association withthe sport if its UCI governing body failed to act on doping.

Its Chief Executive Jaimie Fuller warned the commercialfall-out could be worse than the damage suffered by a dopingscandal centred on the Festina team that hit the Tour de Francein 1998.

Cycling has attracted a new generation of sponsors in recentyears who stress their commitment to clean competition.

The sport increasingly appeals to affluent fortysomethingswho want to stay active for longer - earning it the nickname"the new golf" and boosting its commercial appeal.

British team Sky, sponsored by pay-TV company BSkyB,said this week it would sack team members unless they signed adocument saying they had never doped. Sky rider Bradley Wigginsthis year became the first Briton to win the Tour.

The Rabobank cycling team, which has taken part in everysingle Tour de France since 1984, said in a statement itregretted but understood the bank's decision.

"We've been cycling for 17 years now with the name Rabobankproudly on our shirts, and it hurts that going forward we'llhave to do without that name," it said.

Its top riders are Dutchman Robert Gesink, this year's Tourof California winner, and Spaniard Luis Leon Sanchez, winner offour Tour de France stages.

Some critics said Rabobank was using Armstrong as an excuseto cut spending on sports sponsorship.

"Fact that Rabobank decision includes the women's teamsuggests that it's a commercial decision not an ethical one.USADA provided excuse," Irish former Olympic coach Dave Smithsaid on Twitter.